With increasing population sizes, costs per unit of energy, and the size and type of energy consuming devices used by consumer's today, there are increasing interests in optimizing consumers' use of energy. While typical consumer's use energy via a variety of mechanisms, heating, ventilation, and air conditioning (HVAC) systems are good candidates to direct optimization efforts as they account for up to 40% of energy consumption needs of an average consumer in the United States. Techniques for reducing the amount of energy consumed by such systems may thus advantageously result in tangible energy reductions and cost savings on an individual basis, and significant reductions in energy demand in the aggregate.
In many modern HVAC systems, the HVAC system can be controlled as a schedule of events. For example, a user may select a schedule of temperatures (i.e., temperature setpoints) that the user desires the HVAC system to control the indoor temperature to be. Such a schedule of temperature setpoints may define temperatures at which the HVAC system controls the indoor temperature of the structure when the user is home, away, sleeping, or awake. That is, the indoor temperature can be controlled for any and all times of the day, regardless of occupancy.
While implementation of a schedule of temperature setpoints by an HVAC system typically leads to a user being satisfied with the indoor temperature of the structure at any given time, the temperatures defined by the schedule may not reach the nexus between the user being comfortable and the user being uncomfortable. That is, there may be some difference in temperature between what the user set as being comfortable and at which the user is actually comfortable. Known HVAC control systems are typically strict in their adherence to the users requests for a specific schedule of temperature setpoints without concern to such possible differences, resulting in the potentially unnecessary consumption of energy. In addition to the strict adherence to the temperature-wise characteristics of a schedule of temperature setpoints (i.e., adherence to the temperature magnitudes set by the user), typical HVAC control systems are similarly strict in their adherence to the time-wise characteristics of a schedule of temperature setpoints (i.e., strict adherence to the time for which a temperature setpoint is defined by the user). Such inflexibility may result in additional inefficiencies in a variety of situations, such as when the real time price of energy consumption changes throughout the day.